Inbred corn like PHK29

ABSTRACT

According to the invention, there is provided a novel inbred corn line, designated PHK29. This invention thus relates to the seeds of imbred corn line PHK29, to the plants of inbred corn line PHK29, and to methods for producing a corn plant produced by crossing the inbred line PHK29 with itself or another corn line. This invention further relates to hybrid corn seeds and plants produced by crossing the inbred line PHK29 with another corn line.

FIELD OF THE INVENTION

This invention is in the field of corn breeding, specifically relating to an inbred corn line designated PHK29.

BACKGROUND OF THE INVENTION

The goal of plant breeding is to combine in a single variety/hybrid various desirable traits of the parental lines. For field crops, these traits may include resistance to diseases and insects, tolerance to heat and drought, reducing the time to crop maturity, greater yield, and better agronomic quality. With mechanical harvesting of many crops, uniformity of plant characteristics such as germination and stand establishment, growth rate, maturity, and fruit size is important.

Field crops are bred through techniques that take advantage of the plant's method of pollination. A plant is self-pollinated if pollen from one flower is transferred to the same or another flower of the same plant. A plant is cross-pollinated if the pollen comes from a flower on a different plant.

Plants that have been self-pollinated and selected for type for many generations become homozygous at almost all gene loci and produce a uniform population of true breeding progeny. A cross between two homozygous plants from differeing backgrounds or two homozygous lines produce a uniform population of hybrid plants that may be heterozygous for many gene loci. A cross of two plants each heterozygous at a number of gene loci will produce a population of hybrid plants that differ genetically and will not be uniform.

Corn plants (Zea mays L.)can be bred by both self-pollination and cross-pollination techniques. Corn has male flowers, located on the tassel, and female flowers, located on the ear, on the same plant. Natural pollination occurs in corn when wind blows pollen from the tassels to the silks that protrude from the tops of the incipient ears.

The development of commercial corn hybrids requires the development of homozygous inbred lines, the crossing of these lines, and the evaluation of the crosses. Pedigree breeding and recurrent selection breeding methods are used to develop inbred lines from breeding populations. Breeding programs combine desirable traits from two or more inbred lines or various broad-based sources into breeding pools from which new inbred lines are developed by selfing and selection of desired phenotypes. The new inbreds are crossed with other inbred lines and the hybrids from these crosses are evaluated to determine which have commercial potential.

Pedigree breeding starts with the crossing of two genotypes, each of which may have one or more desirable characteristics that is lacking in the other or which complement the other. If the two original parents do not provide all of the desired characteristics, other sources can be included in the breeding population. In the pedigree method, superior plants are selfed and selected in successive generations. In the succeeding generations the heterozygous condition gives way to homogeneous lines as a result of self-pollination and selection. Typically in the pedigree method of breeding, five or more generations of selfing and selection is practiced: F₁ →F₂ ; F₂ →F₃ ; F₃ →F₄ ; F₄ →F₅ ; etc.

Backcrossing can be used to improve an inbred line. Backcrossing transfers a specific desirable trait from one inbred or source to an inbred that lacks a trait(s). This can be accomplished for example by first crossing a superior inbred (A) (recurrent parent) to a donor inbred (non-recurrent parent), which carries the appropriate gene(s) for the trait in question. The progeny of this cross is then mated back to the superior recurrent parent (A) followed by selection in the resultant progeny for the desired trait to be transferred from the non-recurrent parent. After five or more backcross generations with selection for the desired trait, the progeny will be heterozygous for loci controlling the characteristic being transferred, but will be like the superior parent for most or almost all other genes. The last backcross generation would be selfed to give pure breeding progeny for the gene(s) being transferred.

A hybrid corn variety is the cross of two inbred lines, each of which may have one or more desirable characteristics lacked by the other or which complement the other. The hybrid progeny of the first generation is designated F₁. In the development of hybrids only the F₁ hybrid plants are sought. The F₁ hybrid is more vigorous than its inbred parents. This hybrid vigor, or heterosis, can be manifested in many ways, including increased vegetative growth and increased yield.

The development of a hybrid corn variety involves three steps: (1) the selection of superior plants from various germplasm pools; (2) the selfing of the superior plants for several generations to produce a series of inbred lines, each of which, although different from each other, bred true and are highly uniform; and (3) crossing the selected inbred lines with unrelated inbred lines to produce the hybrid progeny (F₁). During the inbreeding process the vigor of the line decreases. Vigor is restored when two unrelated inbred lines are crossed to produce the hybrid progeny (F₁). An important consequence of the homozygosity and homogeneity of the inbred lines is that essentially all the hybrid plants resulting from a cross between any two inbreds will be genetically uniform. Once the inbreds that give the best hybrid have been identified, the hybrid seed can be reproduced indefinitely as long as the homogeneity of the inbred parent is maintained.

A single-cross hybrid is produced when two inbred lines are crossed to produce the F₁ progeny. A double-cross hybrid is produced from four inbred lines crossed in pairs (A×B and C×D) and then the two F₁ hybrids are crossed again (A×B) ×(C×D). Much of the hybrid vigor exhibited by F₁ hybrids is lost in the next generation (F₂). Consequently, seed from hybrid varieties is not used for planting stock.

Corn is an important and valuable field crop. Thus, a continuing goal of plant breeders is to develop stable, high-yielding corn hybrids that are agronomically sound. The reasons for this goal are obvious: to maximize the amount of grain produced on the land used and to supply food for both animals and humans. To accomplish this goal, the corn breeder must select and develop corn plants that have the traits that result in superior inbred parental lines for producing hybrids.

SUMMARY OF THE INVENTION

According to the invention, there is provided a novel inbred corn line, designated PKH29. This invention thus relates to the seeds of inbred corn line PHK29, to the plants of inbred corn line PHK29, and to methods for producing a corn plant produced by crossing the inbred line PHK29 with itself or another corn line. This invention further relates to hybrid corn seeds and plants produced by crossing the inbred line PHK29 with another corn line.

DEFINITIONS

In the description and examples that follow, a number of terms are used herein. In order to provide a clear and consistent understanding of the specification and claims, including the scope to be given such terms, the following definitions are provided:

Predicted RM. This trait, predicted relative maturity (RM), for a hybrid is based on the harvesrt moisture of the grain. The relative maturity rating is based on a known set of checks and utilizes standard linear regression analyses and is referred to as the Minnesota Relative Maturity Rating System.

MN RM. This represents the Minnesota Relative Maturity Rating (MN RM) for the hybrid and is based on the harvest moisture of the grain relative to a standard set of checks of previously determined MN RM rating. Regression analysis is used to compute this rating.

Selection Index. The selection index gives a single measure of the hybrid's worth based on information for up to five traits. A corn breeder may utilize his or her own set of traits for the selection index. One of the traits that is almost always included is yield. The selection index data presented in the tables in the specification represent the mean value averaged across testing stations.

Yield (Bushels/Acre). The yield in bushels/acre is the actual yield of the grain at harvest adjusted to 15.5% moisture.

Percent Yield. The percent yield is the yield obtained for the hybrid in terms of percent of the mean for the experiments in which it was grown.

Moisture. The moisture is the actual percentage moisture of the grain at harvest presented in percent of the mean for the experiments in which the hybrid was grown.

GDU Shed. The GDU shed is the number of growing degree units (GDU) or heat units required for an inbred line or hybrid to reach anthesis or pollen shed from the time of planting. Growing degree units are calculated by the Barger Method, where the heat units for a 24-hour period are: ##EQU1## The highest maximum used is 86° F. and the lowest minimum used is 50° F. For each hybrid it takes a certain number of GDUs to reach various stages of plant development. GDUs are a way of measuring plant maturity. The data is given in percent of the mean for the experiments in which the hybrid was grown.

Stalk Lodging. This is the percentage of plants that do not stalk lodge, i.e., stalk breakage, as measured by either natural lodging or pushing the stalks and determining the percentage of plants that break off below the ear. This is a relative rating of a hybrid to other hybrids for standability. The data are given as the percentage of the mean for the experiments in which the hybrid was grown.

Root Lodging. The root lodging is the percentage of plants that do not root lodge; i.e., those that lean from the vertical axias at an approximate 30° angle or greater would be counted as root lodged. The data is given in percentage of mean of the experiments in which the hybrid was grown.

Barren Plants. This is the number of the plants per plot that were not barren (lack ears). The data is converted to percent of the mean for the experiments in which the hybrid was grown.

Stay Green. Stay green is the measure of plant health near the time of black layer formation (physiological maturity). A high score indicates better late-season plant health. The data is given in percentage of mean of the experiments in which the hybrid was grown.

Test Weight. This is the measure of the weight of the grain in pounds for a given volume (bushel) adjusted for percent moisture. The data is given in percentage of mean of the experiments in which the hybrid was grown.

Cob Score. The cob score is a rating of how well the grain is shelled off the cob and how badly the cob is broken up going through the combine. This is given as a 1 to 9 score with 9 being good. A high score indicates that the grai shells off of the cob well, and the cob does not break. The data is given in percentage of mean of the experiments in which the hybrid was grown.

Grain Quality. This is a 1 to 9 rating for the general quality of the shelled grain as it is harvested based on the color of the harvested grain, any mold on the grain, and any cracked grain. High scores indicate good grain quality. The data is given in percentage of mean of the experiments in which the hybrid was grown.

Seedling Vigor. This is the visual rating (1G9 score) of the amount of vegetative growth after emergence at the seedling stage (approximately five leaves). A higher score indicates better vigor. The data is given in percentage of mean of the experiments in which the hybrid was grown.

Early Stand Cont. This is a measure of the stand establishment in the spring and represents the number of plants that emerge on a per-plot basis for the hybrid. The data is given in percentage of mean of the experiment in which the hybrid was grown.

Plant Height. This is a measure of the height of the hybrid from the ground to the tip of the tassel and is measured in inches. The data is given in percentage of mean of the experiments in which the hybrid was grown.

Ear Height. The ear height is a measure from the ground to the ear node attachment and is measured in inches. The data is given in percentage of mean of the experiments in which the hybrid was grown.

Dropped Ears. This is a measure of the number of dropped ears per plot and represents the number of plants that did not drop ears prior to harvest. The data is give in percentage of mean of the experiments in which the hybrid was grown.

Brittle Stalks. This is a measure of the stalk breakage near the time of pollination of the hybrids, and is an indication of whether a hybrid would snap or break at the time of flowering under severe winds. Data are presented as percentage of plants that did not snap. The data is give in percentage of mean of the experiments in which the hybrid was grown.

DETAILED DESCRIPTION OF THE INVENTION

Inbred corn line PHK29 is a yellow dent corn with superior characteristics and provides an excellent parental line in crosses for producing first generation (F₁) hybrid corn. Inbred corn lie PHK29 was selected from the cross B47/AC54 through pedigree ear to row selection and selfing. The cross, B47/AC54, was first made at York, Nebr. Both B47 and AC54 are proprietary inbreds of Pioneer Hi-Bred International, Incorporated. The cross, B47/AC54, was selfed in Homestead, Fla., at the winter nursery. The F2 seed from this cross was grown at York, Nebr., and standard ear to row pedigree selfing and selection were practiced for uniformity and agronomic rraits during the line development process. Test crosses were made to several testers and evaluated for general and specific combining ability by the York Corn Research Station. PHK29 proved to have good test cross performance and appeared to have acceptable male and female parental characteristics. At the F7 generation, the line was evaluated by a number of research stations across the Corn Belt both as a line per se and in hybrid combinations. One particular cross showed outstanding performance in the York corn research testing. This hybrid was evaluated extensively in research testing at numerous Pioneer Research Stations.

The inbred is adapted over most of the Corn Belt, but it does have better performance in the western area. However, in specific combinations, its performance has been outstanding across most of the Corn Belt. This inbred can advantageously be used in hybrids of approximately 107 through 128 relative maturity based on the Minnesota Relative Maturity Rating System for harvest moisture of grain. The inbred is a good female and over 289 reps of per se data, PHK29 has yielded 12% more than B73, a popular public female in the corn industry. Also, the inbred has better cold test and better size out than B73 in research testing. PHK29 has been observed to silk ball in seed production fields and the frequency of silk balling has been in the range of 5% to 20% when it occurs. This has appeared to have little detrimental affect on performance as the line yields well relative to other inbred lines and produces pure seed with proper isolation. The inbredcould be used as a male; in over 13 locations PHK29 averaged 1.24 grams of pollen per plant which would be 93% of the mean for the experiments it was in. It should shed adequate pollen to be utilized as a male parent in hybrid production.

The inbred has shown uniformity and stability for all traits as described in the following variety description information. It has been self-pollinated and ear-rowed a sufficient number of generations with careful attention paid to uniformity of plant type to insure homozygosity and phenotypic stability. The line has been increased both by hand and in isolated fields with continued observations for uniformity. No variant traits have been observed or are expected in PHK29.

Inbred corn line PHK29 has the following morphological and other characteristics (based primarily on data collected at Johnston, Iowa):

    ______________________________________                                         PHK29                                                                          VARIETY DESCRIPTION INFORMATION                                                ______________________________________                                         A.  Maturity: Zone 6: mid-season or Corn Belt                                      INBRED = PHK29                                                                 Heat Unit Shed: 1520                                                           Heat Unit Silk: 1540                                                           No. Reps: 46                                                                   Heat Units =                                                                    ##STR1##                                                                  B.  Plant Characteristics                                                          Plant height (to tassel tip): 245 cm                                           Length of top ear inner node: 6 cm                                             Number of ears per stalk: Single                                               Ear height (to base of top ear): 92 cm                                         Number of tillers: None                                                        Cytoplasm type: Normal                                                     C.  Leaf                                                                           Color: Dark green (B14)                                                        Angle from stalk: 30°-60°                                        Marginal waves: Few (WF9)                                                      Number of leaves (mature plant): 21                                            Sheath pubescence: Light (W22)                                                 Longitudinal creases: Absent (OH51)                                            Length (ear node leaf): 86 cm                                                  Width (widest point, ear node leaf): 11 cm                                 D.  Tassel                                                                         Number of lateral branches: 3                                                  Branch angle from central spike: >45°                                   Pollen shed: Heavy-- parent test data would classify it medium                 Peduncle length (top leaf to basal branches): 29 cm                            Anther color: Observed yellow, secondary pale purplish-red                     Glume color: Green                                                         E.  Ear (Husked Ear Data Except When Stated Otherwise)                             Length: 16 cm                                                                  Weight: 121 gm                                                                 Midpoint diameter: 41 mm                                                       Silk color: Green                                                              Husk extension (harvest stage): 8-10 cm                                        Husk leaf: Long >15 cm                                                         Taper of ear: Extreme                                                          Position of shank (dry husks): Horizontal                                      Kernel rows: Number = 14, distinct, straight                                   Husk color (fresh): Dark green                                                 Husk color (dry): Buff, observed light yellow                                  Shank length: 10 cm                                                            Shank (no. of internodes): 6                                               F.  Kernel (Dried)                                                                 Size (from ear midpoint):                                                      Length: 11 mm                                                                  Width: 8 mm                                                                    Thick: 4 mm                                                                    Shape grade (% rounds): <20                                                    Pericarp color: Colorless                                                      Aleurone color: Homozygous, tan--observed orange-yellow                        Endosperm color: Yellow                                                        Endosperm type: Normal starch                                                  Gm Wt/100 seeds (unsized): 24 gm                                           G.  Cob                                                                            Diameter at midpoint: 22 mm                                                    Strength: Strong                                                               Color: Red                                                                 H.  Diseases                                                                       Northern Leaf Blight: Susceptible                                              Goss's Bacterial Blight: Resistant                                             Southern Leaf Blight: Susceptible                                              Head Smut: Resistant                                                           Maize Dwarf Mosaic: Susceptible                                                Common Smut: Resistant                                                         Stewart's Bacterial Wilt: Resistant                                        I.  Insects                                                                        Corn borer: Susceptible                                                        Rootworm (western): Susceptible                                            ______________________________________                                          *If maximum is greater than 86° F., then 86 is used if minimum is       less than 50, then 50 is used. Heat units accumulated daily and cannot be      less than 0.                                                             

Inbred corn line PHK29 most closely resembles B73 in maturity characteristics and B47 in plant type, ear type, kernel type, and usage characteristics.

This invention is also directed to methods for producing a corn plant by crossing a first parent corn plant with a second parent corn plant wherein the first or second parent corn plant is the inbred corn plant from the line PHK29. Further, both first and second parent corn plants may be from the inbred line PHK29. Thus, any methods using the inbred corn line PHK29 are part of the invention: selfing, backcrosses, hybrid breeding, and crosses to populations. Any plants produced using inbred corn line PHK29 are within the scope of this invention. Advantageously, the inbred corn line is used in crosses with other corn varieties to produce first generation (F₁) corn hybrid seed and plants with superior characteristics.

As used herein, the term "plant" includes plant cells, plant protoplasts, plant cell of tissue culture from which corn plants can be regenerated, plant calli, plant clumps, and plant cells that are intact in plants or parts of plants, such as pollen, flowers, kernels, ears, cobs, leaves, husks, stalks, and the like.

Tissue culture of corn is described in European Patent Application, publication number 160,390, incorporated herein by reference. Corn tissue culture procedures are also described in Green and Rhodes, "Plant Regeneration in Tissue Culture of Maize," Maize for Biological Research (Plant Molecular Biology Association, Charlottesville, Va. 1982), at 367-372. Thus, another aspect of this invention is to provide for cells which upon growth and differentiation produce the inbred line PHK29.

USES OF CORN

Corn is used as human food, livestock feed, and as raw material in industry. The food uses of corn, in addition to human consumption of corn kernels, include both products of dry- and wet-milling industries. The principal products of corn dry-milling are grits, meal, and flour. The corn wet-milling industry can provide starch, syrups, and dextrose for food use. Corn oil is recovered from corn germ, which is a by-product of both dry- and wet-milling industries.

Corn is also used extensively as livestock feed primarly to beef cattle, dairy cattle, hogs, and poultry.

Industrial uses of corn are mainly from corn starch from the wet-milling industry and corn flour from the dry-milling industry. The industrial applications of corn starch and flour are based on functional properties, such as viscosity, film formation, adhesive properties, and ability to suspend particles. The corn starch and flour have application in the paper and textile industries. Other industrial uses include applications in adhesives, building materials, foundry binders, laundry starches, explosives, oil-well muds, and other mining applications.

Plant parts other than the grain of corn are also used in industry. Stalks and husks are made into paper and wallboard and cobs are used for fuel, to make charcoal.

The seed of inbred corn line PHK29, the plant produced by the inbred seed, the hybrid corn plant produced from the crossing of the inbred, hybrid seed, and various parts of the inbred and hybrid corn plant can be utilized for human food, livestock feed, and as a raw material in the industry.

EXAMPLES

In the examples that follow, the traits and characteristics of inbred corn line PHK29 are given as a line and in hybrid combination. The data collected on inbred corn line PHK29 is presented for the key characteristics and traits.

Example 1

The data in Table 1 shows the relative hybrid performance of PHK29 to B73 which is a public inbred developed by Iowa State University and has been widely used in the industry as a parent in numerous hybrid combinations. This data was obtained across 11 inbred testers and six Pioneer Corn Research Stations. The data was averaged across all testers and replicatons for PHK29 and B73. In other words, the crosses were evaluated in the same experiments when PHK29 and B73 were crossed to a common tester. The data shows that PHK29 produces hybrids with slightly lower yields but that are 4% drier on the average and that shed about the same time as B73 hybrids. PHK29 makes hybrids that have much better root lodging resistance than B73 and tend to have better stay green characteristics. Although PHK29 hybrids were a little taller, they were 4% lower earred. This performance data coupled with the production advantage of PHK29 over B73 make it a very important inbred for producing single cross hybrids.

In specific combinations, PHK29 has shown outstanding yield performance in hybrid combination relative to other commercially sold hybrids of similar maturity.

                                      TABLE 1                                      __________________________________________________________________________     Average Inbred by tester performance comparing PHK29 to B73 crossed to         the same inbred testers and grown in the same experiments. All values          expressed as percent of the experiment mean except Predicted RM, Selec-        tion Index and Yield (BU./AC.).                                                __________________________________________________________________________              PREDICTED                                                                              SELECTION                                                                              YIELD PERCENT       GDU STALK  ROOT                   HYBRID   RM      INDEX   (BU./AC.)                                                                            YIELD  MOISTURE                                                                              SHED                                                                               LODGING                                                                               LODGING                __________________________________________________________________________              No. Reps                                                                       104     108     108   108    108     28 102     64                    PHK29 Crosses                                                                           117     102     158   102     98    100  98    101                    B73 Crosses                                                                             121     101     162   105    102    100 100     86                    DIFFERENCE                                                                               4       1       4     3      4      0   2      15                    __________________________________________________________________________                                            EARLY                                            BARREN                                                                               STAY TEST  COB  SEEDLING                                                                               STAND                                                                               PLANT EAR   DROPPED                HYBRID   PLANTS                                                                               GREEN                                                                               WEIGHT                                                                               SCORE                                                                               VIGOR   COUNT                                                                               HEIGHT                                                                               HEIGHT                                                                               EARS                   __________________________________________________________________________              No. Reps                                                                        6     86  108   10   52      92     66   66    86                    PHK29 Crosses                                                                           100   105   99   75   98      98   102   101    99                    B73 Crosses                                                                             101    99  100   85   95      99   101   105   100                    DIFFERENCE                                                                               1     6    1    10    3       1    1     3     1                     __________________________________________________________________________

Example 2

The data in Table 2 shows the electrophoresis results for PHK29 compared to B47, AC54, and B73 for 19 loci. These tests were based on 10 plants for each inbred.

                  TABLE 2                                                          ______________________________________                                         Electrophoresis results for PHK29                                              compared to B47, AC54, and B73                                                          Alleles Present                                                       Locus      PHK29   B47        AC54  B73                                        ______________________________________                                         Acp1       4       4          2     2                                          Adh1       4       4          4     4                                          Cat3       9       9          9     9                                          Got1       4       4          4     4                                          Got2       4       4          4     4                                          Got3       4       4          4     4                                          Idh1       4       4          4     4                                          Idh2       4       6          4     4                                          Mdh1       6       6          6     6                                          Mdh2       3.5     3.5        3.5   3.5                                        Mdh3       16      16         16    16                                         Mdh4       12      12         12    12                                         Mdh5       12      12         12    12                                         Mmm        --      --         --    --                                         Pgm1       9       9          9     9                                          Pgm2       4       4          4     4                                          Pgd1       3.8     2          3.8   3.8                                        Pgd2       5       5          5     5                                          Phi1       4       4          4     4                                          No. plants 10      10         10    10                                         ______________________________________                                    

Deposit Information

Inbred seeds of PHK29 have been placed on deposit at the American Type Culture Collection (ATCC), Rockville, Md. 20852, under deposit accession number 40416 on Jan. 13, 1988. A Plant Variety Protection Certificate has also been applied for with the U.S. Department of Agriculture.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity and understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the invention, as limited only by the scope of the appended claims. 

What is claimed is:
 1. An inbred corn line designated PHK29.
 2. A plant or plants of the inbred corn line designated PHK29 of claim
 1. 3. Pollen of the plant of claim
 2. 4. Seed or seeds of the inbred corn line designated PHK29 of claim
 1. 5. An inbred cor plant with the phenotypic physiological and morphologic characteristics of inbred corn line designated PHK29.
 6. A method for producing a corn plant comprising crossing a first parent corn plant with a second parent corn plant wherein said first or second parent corn plant is the inbred corn plant having designation PHK29.
 7. The method of claim 6, wherein said first and second parent corn plants are both from the inbred corn line designated PHK29.
 8. A first generation (F₁) hybrid corn plant produced by crossing a first inbred female corn plant with a second inbred male corn plant, wherein said first or second parent corn plant is the inbred corn plant having the designation PHK29.
 9. The hybrid corn plant of claim 8, wherein said inbred corn plant having the designation PHK29 is the female parent.
 10. The hybrid corn plant of claim 8, wherein said inbred corn plant having the designation PHK29 is the male parent.
 11. A method for producing first generation (F₁) hybrid corn seed comprising crossing a first inbred parent corn plant with a second inbred parent corn plant, wherein said first or second parent corn plant is the inbred corn plant having the designation PHK29, to produce first generation (F₁) hybrid corn seed.
 12. A first generation (F₁) hybrid corn plant produced by growing said hybrid corn seed of claim
 11. 